Seismic record display and re-recording



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ATTORNEY Aug. 23, 1960 Original Filed Aug. 50, 1951 G. B. LPER ETALSEISMIC RECORD DISPLAY AND Rza-RECORDING 6 Sheets-Sheet 4 /FESET A/V/VELSYSTEM '25H0 TUBE RESET CHANNEL R//va 00u/WER T/ME BASE CHAN/VEL S/G/VALCHANNELS GEORGE B. L UPEI? ROBERT l?. P/ TTMA/V INVENTORS A T TUR/VE YBNN INVENTORS BY ATTORNEY 6 Sheets-Sheet 5 Qi www.

GEORGE B. LOPE R ROBERT R. P/ T TMAN G B LOPER ETAL SEISMIC RECORDDISPLAY AND RFI-RECORDING Aug. 23, 1960 Original Filed Aug. 30, 1951 G.B. LOPER ET AL SEISMIC RECORD DISPLAY AND REI-RECORDING Aug. 23, 1960 6Sheets-Sheet 6 Original Filed Aug. 30, 1951 Sw mmm lkw am EN [Vw t mmm@M ll Bw llmwumwlJuWw www W Gm @www ummm @www vor* GEORGE B L OPERROBERT R. P/ TTMAN .NVENTORS BYAQMW ATTORNEY United States Patent OSEISMIC RECORD DISPLAY AND RE-RECORDXNG George B. Loper, Dallas, Tex.,and Robert R. Pittman` Tulsa, Okla., assignors, by mesne assignments, toSocony Mobil Oil Company, Inc., a corporation of New York Continuationof applications Ser. No. 244,386, Aug. 30,

1951, and Ser. No. 297,804, July 9, 1952. This application Oct. 2.7,1953, Ser. No. 388,582

25 Claims. (Cl. 340-15) This invention relates to the study of transientwaves recorded in phonographically reproducible form and moreparticularly to a system for producing a visual display and secondaryrecordings of seismic data to facilitate study of records such as areproduced in seismic exploration for the location of structures possiblycapable of or likely to contain accumulations of petroleum.

This application is a continuation of applicants copending applicationsSerial No. 244,386 led August 30, 1951 for Seismic Record Display Systemand Serial No. 297,804 led July 9, 1952 for lle-Recording of SeismicRecords, both now abandoned.

It is customary to detonate an explosive charge near the surface of theearth at a sending station for the generation of seismic waves whichtravel from the point of generation to subsurface reflecting interfaceswhere a portion of the energy is reilected back to the earths surface.Electrical signals generated in response to resulting earth vibration ata plurality of points spaced along the earths surface from the sendingstation are preferably recorded such that the vertically travelingenergy rettlected from subsurface beds appears in bold relief on theresulting seismic record.

In many areas rellected energy often does not appear as distinctly as inareas where both surface and subsurface conditions are more nearly idealfor seismic exploration. Consequently, seismic efforts are oftenfruitless.

In order successfully to seismically explore such areas it has beenproposed to record earth vibrations in the period immediately followingdetonation of the explosive charge undistorted and in phonographicallyreproducible form. With such a record 10, Fig. l, there may then beperformed various operations such yas ltering, phasing and/or mixing ofthe signals as they are reproduced or played back in order to producesecondary records such .as record a. A plurality of secondary recordsmay thus be made from a single primary record to present ydata relatingto the subsurface lithology more clearly 'than ordinarily is possibleusing the conventional techniques.

ln accordance with the present invention there is pro` vided a systemfor studying a primary seismic record 10 -of transient waves 11 having`associated therewith a periodic time base signal 12, and initial marker13 in predetermined time-relation to the instant of generation of thetransient. The system' includes means 14 for cyclically scanning therecord 10 repeatedly to produce on a scaled time base a first signalcorresponding to the transient fwave, a second signal corresponding tothe periodic time base signal and a third signal coincident andcorresponding with the initial time marker. A monitoring unit 15 havinga signal channel 16 and a control channel 17 is connected to thescanning means for application of the transient lto the monitoring unitsignal channel. A normally non-conductive unit 18, connected to thescanning means, is responsive only to the second signal. A circuit 19responsive to the third or the initial 'marker signal is connectedvbetween the scanning means Patented Aug, 23, 1960 rice l and thenon-conductive circuit to render it conductive during each cycle of thetransient or rst signal at a time coincident with the timing marker. Acounter or pulse selecting circuit 20 is connected between the normallynon-conductive unit and the control channel of the monitoring means toapply to the control channel a selected cycle of the second signal toactuate the monitoring means and render it responsive to the firstsignal. Means 21 operable in the interval following the selected cycleof the second signal and the beginning of the next succeeding cycle ofthe iirst signal renders non-conductive the unit responsive to thesecond signal.

In accordance with a further aspect of the invention there is providedautomatic reset means for a. ring counter or pulse divider system. Moreparticularly, in a ring counter system characterized by a plurality ofgas tubes each having a tiring terminal connected to an adjacent tube toform a closed loop in which conduction of current trom va voltage sourceis shifted sequentially from tube to tube around the loop, there isprovided a resistance means in the circuit between the voltage sourceand the anodes of the ring counting tubes together with a high currentnormally non-conductive thyratron which is connected in parallel withthe tubes. The thyratron is connected at its cathode to the negativeterminal of the voltage source and at its anode to the anodes of theling counter tubes. A condenser connected between the anodes of the ringcounter tubes and the negative terminal of the voltage sourceaccumulates a charge proportional to the voltage of the source. A resetpulse is applied to the grid of the thyratron to initiate conduction fordischarge of the condenser in a period depending upon the time constantof the condenser-thyratron circuit whereby the voltage on the anodes ofthe ring counter tubes is lowered during such period beyond the pointthat conduction may be maintained. A circuit responsive to changes inthe voltage at the anode of the thyratron is connected directly to thetiring terminal of a selected one of the ring counter tubes fortransmission of a pulse produced in time-coincidence with theapplication of the reset pulse to the thyratron. Means in the lattercircuit are provided for delaying transmission of the pulse a timeinterval greater than the period of discharge of the condenser toinitiate conduction after such discharge and after recovery of thethyratron.

ln accordance with a further aspect of the invention, there is provideda system for synchronizing with the reproduction of signals on theprimary record the re-recording thereof after selective treatment on aspace scale related to the time-occurrence of the original eventindependently of the speed characteristics of the reproducing and/orrecording elements.

ln accordance with a more specific aspect of the invention a system forre-recording a phonographically reproducible reco-rd of seismic wavestogether with an initial marker recorded coincident with the generationof said seismic waves and with a time base signal is provided whichincludes signal producing means responsive to the record having threeoutput signals corresponding to the record of said seismic waves, saidtime base signal and said timing marker. A transmission channel isprovided for the first of the three output signals to apply the firstoutput signal to a recorder having a recording medium driven past arecording point thereby to impress the tirst of the signals on therecording medium. A normally non-conductive channel is provided for thesecond of the three output signals, and a circuit responsive to thethird of the three output signals is connected to the normallynon-conductive channel to render it conductive coincident with theoccurrence of the third output signal. The normally non-conductivechannel is connected to the re-` corder to apply to the recording mediumfollowing the 3 third signal the second `of' the output signals in aspace relation with respect to the first of the signals the same as thetime base on the original recording as related to the seismic signals.

In accordance with another aspect of the invention a space scale isproduced on a recording medium as it is driven past a recording point bymeans of a pair of transducers positioned adjacent the recording point.Control pulses uniformly repeated in time are applied first to one andthen to the other of the transducers to irnpress low intensityindications on the recording medium at points of a first spacing. Pulsedividing means responsive to the control pulses produces output pulsesat a selected submultiple of the frequency of the control pulses, andthe latter are applied simultaneously to both of said transducers toimpress relatively high intensity indications at points on said mediumof a second spacing related to the first spacing the same as thesubmultiple is related to the frequency of the control pulsesdistinctively to mark the scale.

For a more complete understanding of the present invention and forfurther objects and advantages thereof, reference may now be had to thefollowing description taken in conjunction with the accompanyingdrawings in which:

Fig. l illustrates a seismic display system, portions of which are inblock diagram form;

Fig. 2 is a more detailed schematic diagram of a portion of the systemof Fig. 1;

Fig. 3 is a continuation of the circuit of Fig. 2;

Fig. 4 is a diagram of the two stages of the timing ring of Fig. 3;

Fig. 5 is a simplified block diagram of a display-rerecording system;

Fig. 6 illustrates signal reproducing means and a portion of a timingcontrol network;

Fig. 7 includes elements of the timing control network and there-recording and display means; and

Fig. 8 is a detailed schematic diagram of the timing marker producingmeans.

Referring now to Fig. 1, the six trace seismogram is shown in the formOf a Variable area recording on a transparency such as a photographicrecord film 10. The six transient or signal traces 11 vary in amplitudein accordance with seismic signals received at a corresponding number ofreceiving stations spaced along a line on the surface of the earth inaccordance with conventional seismic practices.

A variable area recording has been adopted for the purpose of thisdescription since the functions to be considered may be graphicallyportrayed more readily than other forms of recording. It will beapparent that other types of phonograpically reproducible records may beutilized in practicing the invention. For example the variations inamplitude on the film 10 may be taken to represent intensity ofmagnetization of a magnetic tape or the modulation of a carrier forrecording on a magnetic tape. Phonographic discs, or variable densityrecords as illustrated in Patent No. 2,051,153 to Rieber, may also befound suitable. The term phonographically reproducible is` thereforegiven in this case the same generic meaning as in the said Rieberpatent.

Since the general procedure for obtaining seismic `records is well knownand understood by those skilled in the art, it will not be describedhere in detail. Briefly, however, -at a sending station spaced from thereceiving stations, anexplosive charge is detonated to produce Seismicwaves, an electrical impulse being generated coincident with thedetonation of the explosive charge. The latter impulse is recorded asthe time break pulse or the initial marker 13 along with the timingsignal 12 on the seventh record trace (the top trace, Fig. 1). The timebreak pulse 13 and the periodic timing signal 12 are utilized accuratelyto measure the time required for energy to travel from theaforementioned sending station to a subsurface reflecting bed and backto the receiving stations. While a relatively high frequency periodictiming signal, i.e. a carefully controlled 1,000 cycle per secondsignal, ordinarily is used, a low frequency sine wave signal has beenhere adopted and shown in Fig. l for the purpose of illustration only,it being representative of the conventionally employed high frequencysignal.

The seismic data recorded on the six traces 11 is characterized byinitially high energy levels corresponding with the arrival of refractedwaves successively at each receiving station and thereafter followed bya relatively quiescent period. In the record interval 25 it will benoted that there is a prominent burst of energy, this energy appearingat an intermediate record time in such a manner as to be generallyindicative of energy reflected from a subsurface bed. That all of thereceiving stations are affected by a given burst of energy atapproximately the same instant after detonation of the explosive isapparent from a mere inspection of the record. However, the reduction ofsuch'information to accurate `data useful in calculating the depth ofthe causal reflecting interface is often an impossible task. This isparticularly true when the seismic energy represented by variations intrace amplitude is singular in character from trace to trace.Seismologists in their interpretation of seismic records relay uponcoincidence not only of the time-occurrence of record energy but alsoupon substantial coincidence in the character of the seismic energy atthe several seismic detecting stations. The sy em illustrated in Fig. l,as will hereinafter appear, is particularly useful in reducing to usefuldata the seismic information from a record that otherwise may not beutilized in determining the location and/or nature of subsurface beds.

By the present invention there is provided a system in which anyselected record interval such as interval 25 may be displayed fordetailed study and wherein the seismic energy occurring in that intervalmay be ino-dified for deriving therefrom a maximum of intelligence.

While the details of the operation of this system will be explained inconnection with Figs. 2 and 3, a more general description will first begiven in connection with Fig. l.

As illustrated in Fig. 1, varying voltages are produced which correspondboth in number and in forni to the signal traces 11 on the record 10.For example, they may be produced by light-sensitive devices housed inthe unit 14 onto which a beam of light from a source 26 is projected.Unit 14 may include a plurality of transducers such as photo-electriccells. The light beam passes through a slit in the housing of source 25and through the record 10 as its travels at substantially constantVelocity past unit 14 in the direction of the arrow 27.

It will be apparent that, although the actual time interval in which theevents on the seismic record occurred during the original recordingthereof is fixed, the study of the resulting seismic record may beperformed at rates slower or faster, depending upon the apparatus usedand not in any way limited to the actual record interval. This, ofcourse, will depend upon the velocity of the record 10 as it travelspast the detector 14. Thus in the following discussion reference will bemade to a scaled time base and a scaled time interval in which anappropirate scaling factor relates frequencies and time to actualphysical conditions characteristic of the original seismic event.

The signals from unit 14 are applied on a scaled time base to themonitoring unit 15, a cathode ray oscilloscope for example, throughseismic signal channels and a multi-circuit switch 35. The seismicsignal channels preferably will include amplifying means 30-35 and lters30a-35:.' selectively to pass desired components of spaanse the signalsfrom the detector 14 as will hereinafter be explained in more detail.

As is understood by those skilled in the art, an electronic switch 36receives a plurality of signals (i.e. from filter 30a-35a) andsequentially transmits the signals to the single input channel 16 of theoscilloscope 15 for presentation on the oscilloscope screen of theseismic signals either in the same form as they appear on the record orselectively modified. It will be apparent that a multi-gun oscilloscopeor monitoring unit may be utilized thereby eliminating the necessity ofthe electronic switch. s

An electrical pulse generated in time coincidence with S0-35 may beadjusted for optimum resolution of the the detonation of the explosivecharge is recorded and appears as the sharp opaque marker 13superimposed upon the constant frequency time base signal 12. The outputof `the transducer in detector 14 responsive to the top record tracecomprises two components. The first component is a constant frequencyperiodic signal which, regardless of the speed at which the record A10is driven, provides a scaled time base voltage for measurement of thetime occurrence on the record 10 of any selected seismic event. Thesecond component is a sharp pulse or initial marker of distinctivecharacter. It is generated once for each complete cycle of the record10, at a scaled record time corresponding with the instant of detonationof the explosive charge. The scaled time base signal is produced byvariations in light passing through the constant frequency portion 12 ofrecord 10 whereas the initial marker is generated by variations in lightdue to the opaque marker 13 adjacent the detector 14.

Voltages including the distinctive initial marker and the time basevoltage are applied to channel 39 leading seismic data. When suchresolution has been accomplished, the permanent record 10a may be madeof the seismic signal, thus modified, upon energization of the recorder45 which may be of the conventional type and which records the pluralityof traces as undulating lines. More particularly, the modied seismicsignals as they appear at the outputs of the amplifying channels areapplied by way of the plurality of circuits 46 to the input terminals ofthe recorder 45.

As will hereinafter be explained, a time scale channel 4'7 interconnectsthe counter 20 and the recorder 45 to provide a time controlled scale onthe secondary record 10a. It will, vbe shown that in accordance with apreferred mode of operation the first timing line 48 on record 10aappears in a space relation relative to the record segment 25h, in thesame relation as the initial marker 13 bears to the interval 25 ofrecord 10. The space relation between line 13 and segment 25 may be sameas between timing line 48 and record segment 25b or they may bedifferent depending upon the scaling from detector 14 land are appliedto a selector or separator which has a single input channel, channel 39,and two output channels, channels 41 and 42. The rst output channel 41selectivelyl transmits the initial marker correspondin-g with therecorded pulse 13 to the circuit 19, a switching unit. Similarly, thechannel 42 selectively transmits the periodic time base voltagecorresponding to the periodic wave 12 to the gating unit 18.

As above mentioned, the periodic timing base signal 12 may be of anyselected carefully controlled frequency. To expedite calculations in thedecimal system a frequency that is a multiple of 10 is preferred. Forthe purpose of the present discussion, it will be assumed that theperiodic wave 12 has a frequency of 1,000 cycles per second so that thechannel 42 transmits a scaled 1,000 cycle per second signal to thegating unit 18.

The switching unit 19 may be a bi-stable multivibrator for example whichoperates selectively to render the gating unit 18 conductive ornon-conductive in response to the initial marker pulse 13 thereby tocontrol the intervals during which the periodic time base signal may betransmitted to the gating unit output channel 43.

When the gating -unit 18 is conductive, it serves not only to transmitperiodic timing .pulses to the channel 43 but also to shape them forapplication to and actuation of the counting circuit 20. The periodictime base signal is applied to the counter 2) by channel 43 and is inthe form of 1,000 unidirectional pulses per scaled second intervalwhereas the voltage on the output channel 17 of counter 29 is a singlepulse for actuation of the oscilloscope 15 Counter 2e is essentially aselective time delay network which selects from the periodic time basesignal any selected pulse following the instant that the gating unit 13is rendered cond-uctive. lIt operates as a count down circuit operativeto produce pulse division by a selectable whole number ratio. Theapplication of a single selected pulse to the oscilloscope 15 in eachcycle of reproduction of the seismic record 10 triggers the sweepvoltage generator of the oscilloscope 15 to initiate, for each cycle ofthe record 10, the presentation of a factor inherent in the reproductionand re-recording of the signals on record 10.

As above noted, the record `10 in the form of a continuous loop, carriedby rollers 49 and 49a, is driven at a constant speed by means such as asuitable motor (not shown). The record follows a path closely adjacentthe detector unit 14 repeatedly to reproduce the seismic signals in theform of varying voltages. Following each cycle of signal generation fromdetector 14, the gate 18 and counter 20 `are reset preparatory toreceiving the next succeeding cycle.

A voltage directly related in time to the signal presen tation on theoscilloscope 15, such as the voltage applied to the horizontaloscilloscope plates, for example, is applied by way of channel 50 to thebi-stable multivibrator 19 to actuate the latter and render gate 1Snon-conductive. Additionally, a pulse is applied by way of channel 51and the reset generating circuit 21 to the counter 20. The resetgenerating circuit 21 operates to place the counter 20 in a zero orinitial condition for reception of a succeeding cycle of signals fromthe detector 14.

Additionally, a beam control voltage is applied by way of channel 5S tothe oscilloscope 15, as a beam blanking voltage pulse to suppress thecathode stream and thereby produce a distinctive marker at a known timeafter display interval 25a of the seismic signals in the record interval25.

Now that a general description of operation of the system of Fig. l hasbeen given, the following more detailed description of the variouselements that comprise the systern and the cooperation between theelements will now be helpful in understanding the invention.

The system for producing the signals from the variable area record 10may, for example, take the form generically illustrated in the Patent2,493,519 to Baltosser or t. e Patent 2,463,534 to Hawkins. Otherreproducers for use with different recording mediums similarly areavailable in the art and will be found to be suitable.

The amplifying channels 30-35 may be conventional seismic amplifierswith adjustable filtering means therein. A preferred amplifying systemis illustrated in the application Serial No. 214,553, now U.S. Patent2,725,534, issued November 29, 1955, of William B. Hemphilha co-workerof applicants, for Recording Seismic Waves Without Phase Distortion.Other systems known in the art may be adequate in the treatment andmodication of 7 the seismic signals for the production of secondaryseismic records.

The multi-circuit switch 36 has not been illustrated in detail but maycomprise a ring of freely running monostable multivibrators, eachelement of the ring actuating a gating tube for cyclically andsequentially applying the six seismic signals from channels 30-35 to thesingle input of the oscilloscope 15. Such electronic switching systemsare well known in the art, and consequently it is not deemed necessaryto describe in detail such a circuit. Alternatively, and as above noted,a multi-gun oscilloscope may be used without the need for themulticircuit switch 3,6.

Figs. 2 and 3 illustrate in detail the system for interconnecting theelements above briefly discussed for presenta tion of the display on theoscilloscope in response to and under control of the time break signal13 and the time base signal 12. Figs. 2 and 3 are parts of the samecircuit and should be considered together. Conductors interconnectingthe two figures are similarly labeled in both figures.

Referring first to Fig. 2, one of two conductors forming channel 39 isconnected to a ground terminal 100. The other conductor is connected byway of the conductor 101 to the selector 40. A first circuit in theselector is responsive only to the time base signal and includes aiilter 102 whose output is connected to the gate 18. More particularly,conductor 101 is connected by way of condenser 103 and filterterminating impedance 104 to the low-pass tilter 102. The filter ofconventional type may be an L-C circuit such as illustrated designedselectively' to pass a 1,000 cycle signal, due consideration being givento the time scaling factor. The periodic wave 12, Fig. 1, appears on theoutput conductor 105 from the selector 40 and is applied to the gate 18.

The gate circuit 18 includes an input stage 106 followed by pulseshaping stages 107, 108 and 109. The pulse shaping stages areconventional resistance-capacitance coupled amplifiers. However, onestage, the stage 107, has negative biasing means in its cathode-gridcircuit (a battery 110) for biasing the tube 107 to cut off so that onlythe positive half cycle of the signal applied to its grid is transmittedto tube 108. Such positive half-cycles are then amplified anddifferentiated in the R-C coupling impedances to produce at the anode oftube 109 positive voltage pips recurring at a rate of 1,000 per scaledsecond interval. The anode of tube 109 is coupled by way of conductor 43to the input or control bus 140 of a rst ring counter a (Fig. 3).

The initial marker signal is superimposed on the periodic time basesignal in channel 39 and corresponds to the time break 13 (Fig. 1). Acondenser 115 connected to the grid of a tube 116 passes both the timemarker pulse and the time base signal. The anode of tube 116 isconnected to a filter represented by block 117 which rejects theperiodic time base signal and passes the time marker signal by way ofconductor 124 to the grid of tube 119. The latter tube, together with asimilar tube 118, comprises the bi-stable multivibrator 19. Tubes 118and 119 have their cathodes coupled directly together and connected byway of R-C circuit 120 to ground. The anode of tube 119 is coupled byway of the R-C parallel circuit 121 to -the grid of tube 118. Similarly,the anode of tube 118 is coupled by the IR-IC circuit 122 to the grid oftube 119. The anodes of tubes 118 and 119 are also connected by way ofresistors 123 to the B-lterminal of a suitable source of direct currentvoltage.

The tube 119 normally is in a conducting state. When such is the case,the anode voltage of tube 119 is more negative than the anode of tube118. The anode of tube 118 is coupled by way of conductor 124 and R-Ccircuit 125 to the grid of a triode 126 which forms a part of the gatecircuit 1.8. The cathode of tube 126 is connected directly to thecathode of the gate circuit input tube 106.

The cathode current then flows through the common cathode resistor 127.

In operation when tube 119 of the bi-stable multivibrator is conducting,the grid of tube 126 is at a relatively high positive potential and insuch condition its cathode current flows -through resistor 127 The tube126 having a relatively high current carrying capacity and operating asa cathode follower may control the voltage across resistor 1127. Thecathode of tube 106 is thus maintained at a relatively high positivepotential. The potential of the grid of tube 106 is adjusted to be at orbeyond a cutoff point for tube 106 by selection of the resistors 10-6aand 106b. Resistors 106:1 and 1061; are connected in series between B+and ground. The common juncture therebetween is connected to conductorand the grid of tube 106. Thus, when tube 119 is conducting, no currentflows through tube 106.

However when the initial marker, a voltage pulse of negative polarity,is applied from filter 117 to the grid of tube 119, the current flowtherethrough is stopped. Simultaneously, the feedback of the change ofvoltage at the anode of Itube 119 through the network 121 `to the gridof tube 118 causes tube 118 to begin to conduct. When tube 118 isconducting, its anode potential is driven to a voltage less positivethan when in the non-conducting state. Due to feedback in circuit 122,tube 119 is maintained non-conductive. When tube 118 is conducting, thetime base signal may pass through the gate 18.

Voltage pips produced in `the gating unit 18 and applied by way ofconductor 43 to the counter system 20 are utilized as illustrated inFig. 3 to control the oscilloscope 15. 'I'he counting circuit 20 broadlyis a device for applying a selected voltage pulse to the oscilloscope 15selectively coincident with or at an instant a known interval after theinitial marker. Such interval is an integral multiple of the occurrenceof time-periods of the time base voltage.

In Fig. 3 there are four ring counters, 20a, 20h, 20c and 20d, with onlya part of the first ring shown in detail. They are connected in seriesto permit four-digit control over the interval or delay between theinitial marker and the application of a selected time base pulse to theoscilloscope 15. It will be remembered from the discus sion of Fig. lthat a selected voltage pulse is applied to the oscilloscope 15 toinitiate or actuate the sweep generating voltage for presentation of aselected portion of the signals applied to its signal input terminals.

The ring counters 20a-20d are similar in construction, each being madeup of a ring of ten switching tubes. In Fig. 4 there are illustrated thelocal circuits of two adjacent switching tubes. This circuit and itsoperation fundamentally is as illustrated and described in Wave Forms,M.I.T. Radiation Laboratory Series, vol. 19, McGraw-Hill Book Company,Inc., 1949, particularly at page 612 and illustrated in Fig. 17.10.Quite briey, tube 130 of Fig. 4 has its cathode connected by way of aresistor 131 to ground and to the negative termina1 (B) of a voltagesource. rFhe positive terminal (B+) of the voltage source is connectedto the anode of tube 130. Tube 130 is a thyratron having a control gridand shield. The shield grid is connected by way of a resistor 132 to thenegative terminal of a source whose positive terminal is connected toground, thus maintaining the shield at a high negative potential.Similarly, the shield of the succeeding tube 134 is connected to thenegative terminal of source 133 by way of resistor 13S. The control gridof tube 130 is connected to its cathode and the cathode is connected tothe shield grid of tube 134 by way of a resistor 136. The cathodes oftubes 130 and 134 are interconnected by way of a condenser 137.

The shield grids of both tubes 130 and 134 are connected to a controlbus through signal transmitting elements (condensers 141). The time basepulses on conductor 43 are applied to the bus 140. Assuming that tubes130 and 134 are adjacent tubes in a ring of (n) counters P 9 and thattube 130 is conducting, the next succeeding pulse applied to bus 140Vand through condensers 141 iirestube 134 which raises the potential ofthe cathode thereof. This change in cathode potential coupled to thecathode of tube 130 raises the latter to a point more positive than thepotential of its anode, thus extinguishing tube 130. The next succeedingpulse res the tube following tube 134 and extinguishes tube 134 in asimilar manner.

At the instant tube 134 begins to conduct and tube 130 is extinguished,there is an abrupt change in the DC. level of the cathode voltage onboth tubes. Such changes are utilized, as will hereinafter be explained,for the operation of successive ring counter stages. In Fig. 4 thecathodes of tubes 130 and 134 are connected to adjoining terminals of amulti-position selector switch 150 by way of conductors 142 and 142e,respectively.

Referring again to Fig. 3, it will be seen that tubes 130 and 134 formtwo stages of a ring-of-ten counter, their relationship being preciselythe same as shown in Fig. 4. Only a portion of the ring counter, theportion including the tubes 130, 134 and the additional tubes 143, 144and 146, is illustrated. It will be understood that the portion omittedis constructed after the order of the portion shown. The selector switch150 is manually adjusted to conduct to an output circuit includingresistor 151 and rectifier 151a the change in the cathode voltage of anyselected stage of the ring-of-ten counterV circuit.

The operation of the ring counter will perhaps best be understood byconsidering in detail one cycle of opeeration. Assume at the outset thattube 130 is conducting prior to the generation of the initial marker. Atthis instant it will be remembered that gate 1S is non-conducting sothat there is no signal on the conductor 43.

Coincident With the generation ofthe initial marker, Y

gate 18, Figs. 1 and2, is rendered conductive and the time base signal,1,000 cycle pulses, is applied through gate 18 to the input bus 140,Fig. 4. Each succeeding pulse of the 1,000 cycle time base signalinitiates conduction in one tube of the ring counter and extinguishesthe preceding tube. More particularly, the iirst pulse is effective toiire tube 134 and to extinguish tube 130. The second pulse of the 1,000cycle signal is eiective to .tire tube 143 and extinguish tube 134. Thethird pulse of the 1,000 cycle signal similarly tires tube 144 andextinguishes tube 143. As long as the 1,000 cycle signal appears on thebus 140, the tubes in the ring counter 20a will ire sequentially, thefiring order being tubes 130, 1.34, 143, 144 146 and. 130, etc.

While the firing cycle iscontinuous at a rate dependent upon the 1,000cycle signal, the output from the ring counter 20a is a sub-mutiple ofthe firing rate, and in a ring-of-ten counter the output will have lyothe frequency of the 1,000 cycle signal. For every cycle of operation ofthe ring counter 20a, a signal pulse then appears at the armature of theswitch 150 for transmission through the resistor 151 and the rectifier151a to a pulse shaping circuit 152 which, as indicated in Fig. 3, maybe a monostable multivibrator (M). The output pulses from the ringcounter 20a, shaped by the multi-vibrator 152, are then applied to thering counter 20h, also a ring-often counter, for further reduction inthe output pulse rate. Thus it will be seen that from the 1,000 cyclesignal applied to counter 20a, a 10 cycle signal will appear at theoutput of ring counter 20h. In a similar manner the 10 cycle pulses areapplied to the ring counter 20c to produce 1 cycle pulses forapplication to the ring counter 20d which in turn produces 0.1 cyclepulses for application to the control circuit of the oscilloscope 15. Byutilizing the foregoing count-down circuit, essentially a selective timedelay circuit, the sweep voltage on oscilloscope 15 may be triggered orfired at anly instant following generation of the initial marker signalfrom time break 13 on the seismic record 10. The instant of applicationof a trigger pulse to the oscilloscope 15 must, of course, be located intimeafter. generation o f the initial marker an 10 interval that isequal to an integral multiple of the timing periods of the 1,000 cycletime base signal. The interval may be one equal to or less than theperiod of the time base signal or may be many times the period.

Each of the ring counters has an output selector switch such as switchshown in the counter 20a. If it is desired to view on the oscilloscope15 the portion 25, of the record 10, assumed for the present purpose toappear on the seismic recording during the interval of from 0.5 to 0.6second, the selector switches may be set to initiate display at 0.45second by adjustingthe switches in the following manner. Switch 150 ofring counter 20a will be set on position 0; 20b on position 5; 20c onposition 4; and 20d on position 0.

In order to produce repeated and cyclic presentation of the desiredrecord segment 2S, the ring counters 20a-V 20d must be reset followingeach cycle of scanning of the record and the gate 18 must be closed inorder to set up the next cycle of operation. This function isaccomplished by utilizing a voltage pulse from the oscilloscope 15,preferably a pulse derived from the sweep voltage on the horizontaloscilloscope plates. The sweep voltage conventionally is triangular inform, linearly increasing as a function of time for each presentationand then instantly dropping to a low initial value at the end of eachpresentation. The oscilloscope beam then flies back to its initialposition. The sweep volt-` age, differentiated, is a single pulsepositioned in time at the end of the presentation. A simplediierentiating circuit (not shown) may be utilized to produce a voltagepulse on conductor 50, Fig. 3, which appears in Fig. 2 as appliedthrough circuit 121 to the grid of the tube 118 of mutivibrator 19.

The voltage pulse on conductor 50 being highly negative when applied tothe grid of tube 118 extinguishes tube 118 and at the same time, becauseof the connection through circuit 122 to the grid of tube 119, initiatesconduction therein.

The abrupt change in the voltage level on the anode of tube 118, asabove explained, renders the gate 18 non-conductive. Additionally,another function is performed, the change in anode voltage of tube 118is applied by way of conductors 124 and 162 and condenser 162a to thegrid of tube 163. Tube 163 is the input tube of the reset circuit 21.Tube 163 has its cathode connected directly to ground and is connectedto conductor 165 by way of load resistor 166. The conductor 165electrically is common to the anode circuit of the reset circuit 21 andalso the anode circuits in the gate 18. Conductor 165 also is connectedto a B+ terminal of a suitable DC. source to supply plate voltage to theforegoing tubes.

The anode of tube 163 is connected through resistor 172 and the RCparallel circuit 172a to the grid of a tube 170. The point intermediateresistor 172 and the resistor-condenser circuit 17211 is connected toground through a neon tube 173. A condenser 17351 isvconnected inparallel to the tube 173. The cathode of tube is connected to ground andits anode is connected through a load resistor to the conductor 165.Additionally, the anode is connected by way of condenser 170:1 to theanode of diode 171. The diode 171 is also connected by way of resistor170b to the negative terminal of a D.C. source 170e.

Preferably, tube 163 is a gas filled thyratron, a high current type,having a low plate voltage drop when inV the conducting state.Application to the grid of tube 163 of the voltage change at the anodeof tube 118 fires tube 163. The condenser 163a, connected through aseries resistor to the anode of tube 163 and initially charged to thepotential on the anode of tube 163, discharges through the tube 163. Theconduction period of the tube 163 is determined by the time constant ofthe circuit comprising condenser 163a the series resistor and tube 163.At the end of this period the voltage on the anode of tube 163 is notsuflicient to maintain conduction. Thus tube 163 is extinguished shortlyafter it is fired. As the condenser 16311 recharges, the voltage atpoint 168 rises to the potential on conductor 165. During conduction bytube 163, the voltage at point 168 is at a low level (a conductionvoltage of approximately 8 volts). Since point 168 is the B+ terminalfor al1 of the tubes in the ring counters 20a-20d, the tubes of the ringcounters are all extinguished.

Not only must all of the tubes in the ring counters a-20d beextinguished at the end of each cycle of display on the cathode rayoscilloscope 15, but also a selected initial tube must be firedpreparatory to a succeeding cycle of signals from the seismic record sothat a given portion of the seismic record may be made to appear atprecisely the same position on the face of the oscilloscope tube foreach display cycle. To this end, the change in voltage of anode of tube163 is applied, after a suitable time delay in the circuit 172:1, to thetube 170. The resultant change in anode voltage of tube 170 is coupledby way of condenser 170g, rectifier 171 and the resistor 174 to theshield grid ofthe tube 130 in the ring counter 20a. It will beremembered that the action of tube 163 extinguished all of the tubes inthe ring counters. Therefore application of the single pulse to theshield grid of tube 130 will initiate conduction therein. A similarconnection is provided to apply a similar conditioning pulse to acorresponding tube in each of the ring counters 20h, 20c and 20d so thatin each ring counter the tube having its cathode connected to the zeroposition of its associated output selector switch will be conductingprior to the generation of an initial marker signal for each succeedingcycle of the record 10.

It is to be noted that as the tubes in the ring counters 20a-20d fire insuccession, there is produced a series of pulses appearing between point168, Fig. 2, and ground due to the switching from one tube to another.lf such pulses were allowed to drive the grid of tube 170, resulting intheir application through the reset circuit 171, 174, the otherwiseorderly and cyclic operation of the ring counters would be disrupted. Toprevent such unwanted application of pulses to the reset circuit, theneon tube 173 and its parallel condenser 173a are provided. The neontube 173 has a voltage characteristic such that above a certain voltageit readily conducts and below that voltage it acts as an infiniteimpedance. When tube 163 is non-conducting, the voltage on conductor 165is applied to the neon tube by way of resistors 166 and 172. Thus duringthe period that the ring counters are running, the unwanted pulsesappearing at point 168 are effectively shunted to ground through theconducting neon tube 173 and therefore are not effective on the grid oftube 170 particularly since the resistor 172 has a high value comparedto the resistance of the tube 173 when conducting. The resistor 172 andtube 173 form a voltage sensitive divider, producing voltage division independence upon the state of operation of tube 163. When tube 163 fires,the voltage across the neon tube 173 is lowered to such a relatively lowvalue that it will not conduct. Tube 173 is then a high impedance andthe reset pulse may then be applied to the tube 170.

It will be remembered that the reset pulse itself initiates conductionin tube 163. If, at precisely the same time, the reset pulse passes tothe tube 170, it will appear in the ring counters when the anodevoltages are low. The tubes in the ring counters are not, at thatinstant, capable of conduction. By providing the combination of theresistor-condenser circuit 172a and the condenser 17311 there isproduced a time delay between the instant that the reset pulse firestube 163 and the instant that the reset pulse appears on the grid oftube 170. This time delay is equal to and preferably slightly greaterthan the recovery time of the tube 163. The

latter recovery time is determined by the time constant of the circuitwhich comprises condenser 163a and its series resistor.

The sequence of operations in the above described systern is as follows:

(l) The initial marker renders gate 18 conductive;

(2) The time base signal, the 1,000 cycle signal, is shaped and passedthrough gate 18 to actuate the ring counters;

(3) The seismic signals representing the traces 11 of Fig. 1 are appliedto the signal input circuit of the oscilloscope 15;

(4) At an instant dependent upon the setting of the switches in the ringcounters, the sweep voltage on the oscilloscope 15 is triggeredinitiating display of a selected portion of the seismic record;

(5) At the end of the display period, a pulse is applied to themultivibrator 19 which immediately renders gate 18 non-conductive;

(6) Simultaneously tube 163 is fired dropping the anode voltage on allof the tubes of the ring counters thereby extinguishing all of the ringcounter tubes;

(7) Tube 163 becomes non-conductive following discharge of condenser16311;

(8) The reset pulse, delayed in circuit 17211, is applied after recoveryof tube 163 to the shield grid of the zero tube in each of the ringcounters 20a-20d placing the counters in condition for reception of thenext succeeding cycle of the record 10.

Stated otherwise, the means are provided for studying a phonographicallyreproducible seismogram on which seismic signals and timing signals arerecorded and includes a control system along with the means forcyclically producing electrical signals which correspond with theseismic signals and for concurrently reproducing the timing signal. Thecontrol system includes an electron beam display system with means fordeecting the beam in one sense in concurrence with variations in theelectrical signals together with means for initiating the deilection ofthe beam in a second sense under the control of the timing signal todisplay a desired fraction of the seismogram. A selectively adjustablecontrol is then provided for controlling the instant of initiation ofdeflection in the second sense relative to the instant of initiation ofthe seismic signals.

Referring again to Fig. l, the channel 55 is connected between thecounter 20 and the monitoring means 15 for applying to the monitoringmeans a blanking pulse. While the specific electrical connections havenot been illustrated in the more detailed Figs. 2 and 3, it will beunderstood that the blanking pulse or pulses may be applied momentarilyto stop or shut off the cathode ray at a selected time with respect tothe initial marker 13 on the record 10. It has been found to bepreferable to blank the cathode beam for an instant at scaled recordintervals of 0.1 second thereby to provide an accurate measurement ofthe time occurrence of a specific event on the seismic record as itappears on the screen of the oscilloscope. If desired, a second set ofring counters identical in construction with counters 20a-20d may beutilized to apply a blanking pulse to the cathode ray beam at any timeafter the time break equal to an integral multiple of the period of thetime base signal. With such a system, not only will the display of theseismic record be initiated at a selected instant, but also the timeoccurrence of any event on the displayed portion of the record will beaccurately indicated by the settings of four selector switchesassociated with the ring counters of the blanking pulse producingsystem.

Alternatively, the channel 55 of Fig. 1 may receive a pulse directlyfrom the l cycle counter 20d to blank the cathode beam each 0.1 scaledsecond interval after initiation of the display. By this means thetime-occurrence of any event on the record may be measured without theneed for additional ring counters. The term blanking pulse connotatescomplete momentary suppression of the cathode beam. It will beappreciated that a beam intensifying pulse may also be used as a displaymarker.

' In accordance with another mode of operation in which a blanking pulsefor accurate timing measurement on the displayed portion of the recordis not desired, the sweep trigger, as noted in Fig. 3, may also beapplied to the anode of the tube 118, Fig. 2, to reset the countingsystem at the beginning of the display rather than at the end of thedisplay.

Prom the foregoing it will now be apparent that a selected segment ofrecord 10, Fig. 1, such as segment 25, may be repeatedly presented ordisplayed as segment 25a on oscilloscope 15. For each cycle ofreproduction and display the segment will appear on the oscilloscope inthe same position. This provides a tool whereby an operator may observethe character of the seismic signals on oscilloscope 15 while modifyingby means of suitable lters 30a-35a the amplitude-frequencycharacteristics of the seismic signal channels thereby to produce anoptimum selectivity in so far as a particular record segment isconcerned. The otherwise unintelligible portion 25 of record 10, whenproperly treated, may yield signals highly definitive of reflectedenergy from subsurface beds. Signals of such character may then bepermanently captured or impressed on the record 10a.

It will be apparent that iiexibility ofthe system in selecting theinstant of initiation of the display and the period of the sweep voltageon the oscilloscope 15 makes the system particularly useful. By use of afast sweep, any selected limited portion of the record 10 may bepresented in a highly magnified manner for detailed analysis of suchsegment. If a much slower sweep is utilized, an entire seismogram may bepresented on the face of the oscilloscope. In practice it has been foundpreferable to utilize a sweep on the oscilloscope 15 such as willproduce seismic signal displays of dimensions generally correspondingwith those found on the conventional seismic records such as record 10a.

Having described in detail'the system for'display of an entire recordedtransient phenomena on the record 10 or a portion thereof, there willnow be described a system for producing secondary seismic records suchas record 10a, Fig. 1, particularly where such secondary records areprovided with a time scale which may be relied upon as an accuratemeasure of the original time occurence of reiiected energy appearing onthe secondary record.

Referring to Fig. .5, a block diagram, the system is illustrated asincluding a reproducer 186 having a translating means 181 which has twooutput channels 182 and 183. The seismic signals are transmitted by wayof channel 182Vand selective network 184 to both a visual display means185 and to a re-recorder 186. The initial marker and the time basesignal are transmitted by way of channel 183 to a control unit 187 whichincludes three basic elements. A first unit 188 is adapted to controlthe performance of two subsidiary units 189 and 190. Unit 189 selectsone of the pulses from the time base signal for transmission by way ofchannel 191 to unit 185. Such .pulse is for the purpose of initiatingthe display on unit 185. Unit 190 is adapted to translate a series ofelectrical pulses from the time base signal, beginning with the initialmarker for producing for the re-recorder 186 a timing scale on asecondary record 192.

The system displayed in the block diagram of Fig. is found in detail inFigs. 6, 7 and 8. In considering the latter figures, it should be keptin mind that Figs. 6 and 7, appearing on separate sheets of drawings,are to be taken together as they are parts of a common system forproducing a secondary record. Appropriate interconnecting conductorshave been provided and suitably identified to make clear therelationship between the two figures. Fig. 8 forms one element of thesystem of Figs. 6 and 7.

Referring to Figs. 6 and 7, seismic signals corresponding with traces 11of Fig. 1 are here recorded on a loop of magnetic tape 210 having aplurality oftraces in a side-by-side relationship. Tape 210 is mountedon rollers 211 and 212 which are driven from an external source (notshown) repeatedly and cyclically to drive the record past translatingdevice 213, a multi-head magnetic detector or reproducer. For thepurpose of the present description, the detector 213 will be assumed tohave seven channels, six of which are connected by way of cable 214 toamplifiers 21S-220. Amplifiers 21S-220 may be of the type well known inthe art, each having independently selective frequency characteristiccontrols to produce output signals for application to a recorder 221 asin Fig. 1. A monitoring oscilloscope 222 functionally the same as unit15, Fig. 1, is also connected to the output of amplifiers 21S-220 andsuitably actuated, as above described, repeatedly to present incontrolled graphic array the wave forms of the signals appearing at theoutput of the amplifiers.

. The recorder 221 preferably is of the type utilizing photo-sensitivepaper and includes a plurality of moving coil galvanometers forproducing variable amplitude traces on the record 10a which correspondwith the modified signal outputs of amplifiers 21S-220. Thegalvanometers have not been illustrated since they are well known in theart. By way of example, they may be of the type generically disclosed inExploration Geophysics, Jakosky, Times-Mirror Press, 1940, page 590 etseq.

if the record produced by recorder 221 is to be useful in determiningthe relationship of subsurface reflecting interfaces to the earthssurface, a suitable time scale must be provided on the newly producedrecord. The magnetic record 210 includes not only the above-mentionedsix channels of seismic signals but in addition thereto a seventhchannel having an initial marker and a constant frequency timing basesuch as graphically portrayed on record 10, Fig. 1. As on record 10, theinitial marker and constant frequency timing base, for example a 1,000cycle per second signal, are impressed upon the same track on themagnetic record 210 and are thus reproduced in a common circuit. Theinitial marker and timing base signal appear combined on the channel 225although it is obvious that separate channels could be used.

Thus there are three distinct output signals produced by `translatingdevice 213. The rst output signal corresponds with the recorded seismicsignals. 'Ihe second output signal corresponds with the constantfrequency time base. The third output signal is derived from andcorresponds with the initial marker pulse. The present inventioncontemplates that the initial marker and the time base signal will beutilized to actuate the recorder 221 in such a manner as to produce onthe new seismic record 10a an initial marker and a time base that appearin the same time relation with respect to the modiiied signals fromamplifiers 21S-220 as the original timing marker and the original timebase are related to the original seismic event.

The rate at which the magnetic tape 210 is driven during the originalrecording, in general, will not be the same as the rate at which it isplayed back unless great care is taken both during recording andplayback. In general, variables are introduced such as by changes inlength of the magnetic recording medium under different temperatures and.driving tensions that may not possibly be duplicated upon reproductionof the seismic signals from the magnetic record. By the presentinvention, applicants provide a system for re-recording seismicinformation ina reliable time relationship substantially independent ofmechanical variations introduced by the initial recording system and thereproducing system, thus obviating the necessity for complicated speedcontrol means for the driving mechanisms both in the field recordingsystem and in the playback system.

The seismic signals reproduced from the record 210 1li' stand in ascaled time relation with respect to the original seismic event. Thedesirability of the present invention will be appreciated when it isrecognized that the scaling factor between the original event and thereproduced signals does not ordinarily remain constant. The scalingfactor may be varied over several octaves intentionally for filteringpurposes as in Patent 2,594,767 to Robert P. Green, or it may varyunavoidably in a much more limited manner even though great care istaken to synchronize movement of the magnetic record 210 and therecording medium comprising the record a. Variations of the latternature are insidious, but in either case introduce serious diiculty foran operator or seismic interpreter has no means for detecting the latteror for correcting accurately for either type variation. For example,dimensional variations in the magnetic record 10 in the interval betweenits initial recording and playback may be 'such as to introduceappreciable errors in the production of the secondary record 10a eventhough synchronization of the two records is carefully controlled.

It should be remembered that the ultimate use of the secondary record10a is to determins variations in the depth of reliecting horizons oralternatively to determine variations in the time required for anacoustic signal to travel from the surfacey to such horizons and return.With the velocities of sound ranging from 2,000 to 20,000 feet persecond in earth formations, it is apparent that an error in record timein the order of one-thousandth of a second should be considered serious.Even with careful synchronization, errors of the magnitude of one partin a thousand may readily be introduced. If the record 210 and thesecondary record 10a are not synchronized, variations in the speed ofthe playback system and of the rerecording system will introduce errorsof appreciable magnitude. During the production of a single record suchas record 10a, there may be appreciable variations in the scaling factorwhich relates the time occurrence of the original seismic event to theWaves on a space scale on the record 10a.

By the present invention a time scale is provided for the recorder 221which is reliably related by a scaling factor to the original seismicevent such that the time `scale varies in exactly the same manner asdoes the scaling factor. Thereforey the variations in the scaling factorare compensated for. The secondary records are then wholly independentof variables introduced by the physical yrecording and reproducingsystem.

In references hereinafter made to the timing base and the initialmarker, it will be understood that for the purpose of illustration thetiming base preferably is a recording of a constant frequency signal, asabove assumed to be 1,000 cycles per second on the original recording.The timing marker preferably is a recording of a voltage pulse or othercontrol means corresponding in time with the instant of generation ofthe original seismic waves.

Referring again to Fig. 6, the timing base appears on conductor 225 andis isolated from the initial marker by circuit 227 tuned to 1,000 cyclesper second for application to the input of a gate network 228. As abovedescribed, the time base is transmitted successively through tubes 229,230, 231 and 232. In passing through the channel including tubes229-232, the time base is clipped and differentiated, producing yboth apositive and a negative voltage spike each cycle. By operation of thetube 231 with the battery 231e connected in its grid-cathode circuit,the negative peaks are removed so that at the anode of tube 232, andthus at the output terminal 233, positively polarized unidirectionalpulses appear recurring at the rate of 1,00() per scaled second.

Au additional tube 235 in gate 228 is normally conductive. The cathodecircuit of tube 235 includes a resistor 236 which is common to thecathode circuit of tube 229. When tube 235 is conducting, the voltagedeveloped by reason of current dow through resistor 236 is of 16 suchmagnitude as to maintain tube 229 non-conductive. YIn operation, tube235 is normally conductive and the signal channel of gate 228 normallylis non-conductive but is rendered conductive coincident with productionof the timing marker signal.

More particularly, tube 235 is controlled by a bi-stable multivibrator240 which includes multivibrator tubes 241, 242. The anode of tube 241is connected by way of conductor 243 and lter 244 to the grid of tube23S. Resistor 245 is connected between the grid of tube 235 and ground.In operation, tube 242 is normally in a conducting state. When such isthe case, the anode voltage of tube 242 is more negative than the anodeof tube 241. Thus the grid voltage on tube 235 -is relatively positive,permitting current ow. When the multivibrator 240 is triggered, as byapplication of the initial marker through tube 246 to the grid of tube242, current ow is abruptly terminated in tube 242 and simultaneously isinitiated in tube 241. The initial marker is of amplitude greater thanthe 1,000 cycle timing base. Tube 246 is biased beyond cutoff 'bybattery 247 so to prevent the 1,000 cycle signal from actuating themultivibrator 240 and to permit transmission to multivibrator 240 of theinitial marker only. Current ow in tube 241 maintains tube 242non-conductive thereafter and until a similar pulse is applied to thegrid of tube 241.

When tube 241 is conducting, its anode is driven to a voltage lesspositive than when in the non-conducting state. This voltage, appearingas a voltage change on the grid of tube 235, stops conduction thereinfrom an instant coinciding with generation of the initial marker inchannel 225. When tube 235 ceases to conduct, the cathode bias voltageacross the common cathode resistor 236 is lowered to permit conductionthrough tube 229, thus opening gate 228. The time base pulses thenappear at the terminal 233.

The time base pulses at terminal 233 are applied in Fig. 7 to tire ringcounter 251. Four ring counters, 251, 252, 253 and 254, connected inseries provide a means for controlling transmission of a single pulse toterminal 255 to actuate the sweep circuit of the cathode .rayoscilloscope 222 a predetermined time interval after gate 228 is openedas explained in detail in connection with Figs. 2-4. By suitablyadjusting the controls on the ring counters 251-254, the display onoscilloscope 222 of the seismic signals appearing at the outputs ofamplifiers 21S-220 may be initiated at any desired instant following theinitial marker. By manipulation of the oscilloscope controls and thering counters, the seismic signals may be examined in minute detail ormay be viewed in gross for adjustment of filters in amplifiers 215-220to produce modified seismic signals that are of optimum character. Suchsignals may then be utilized to energize recorder 45.

In order to provide the scale for the record produced by recorder 45,the timing pulses appearing on the input busses 252b and 253b of ringcounters 252 and 253, respectively, are applied to the recorder 45 toproduce impressions on secondary record 10a distinctive in character andrelated in an absolutely predetermined time relation to the initialrecording.

More particularly, each ring counter comprises ten tubes connected incascade. For the purpose of simplicity, only one ring is shown indetail. It is to be noted that the output selector switch 251a in thering counter 251 may be set Aat any one of ten output positions. lf seton the zero position and tube 251C is initially conducting, the rstpulse from gate 228 applied to the input bus 251b will appear directlythrough the output rectifier 251e and 4the output multivibrator 251d forapplication to the input bus 252b of the ring counter 252. lf the switch2510 is set on the rst or the No. l position, the second pulse appliedto the input bus 25ib will appear on the input bus 252. Operation ofeach of the successive ring counters is basically the same so that therecord 10a. vand 259 by means not shown but well known in the elec- 17setting of the selector switch zsm controls the 0.001 second recordtimes. Switch 252a controls the 0.01 second record times. Switch 253acontrols the 0.1 second record times, and the ring counter 254 isactuated in intervals of 1 second.

When the filtering caction is optimum in the amplifiers 21S-220, theselector switches 251a and 252a are set to their zero position so thatupon successive cycles of playback of record 210 pulses will be appliedto channels 258 and 259 every 0.01 second and every 0.1 second,respectively, after the initial marker lrenders the gate 228 conductive.

The pulses on busses 25217 and 25312, occurring at the rate of 100 persecond and 10 per second, respectively, are utilized to impress timingmarkers on the secondary These pulses are inverted in channels 258tronic art. A single stage of amplification, for example, may be used.AThe pulses are applied to the recorder 45 at points 258a and 258i?. Acircuit particularly suitable for producing the timing markers isillustrated in Fig. 8.

In Fig. 8the 0.01 second pulses appearing at terminal 258a are appliedto the input points 260 of a multivibrator 261. Multivibrator 261includes tube 262 whose control grid is connected by way of condenser263 and rectifer 264 to terminal 260. The cathode of tube 262 isconnected directly to the cathode of tube 265 and then is connected toground by way of a resistor-condenser combination 266. The `anode oftube 262 is connected 'by way of circuit 267 to the control grid of tube265, and the control grid of tube 262 is connected to the anode of tube265 by way of circuit 268.

The control grid of tube 265 is connected by way of condenser 269 and`rectifier 270 to terminal 260. The p `ofresistor 273.

Thus the 0.01 second pulses are applied to the grids of both tubes 262and 265. However since tubes 262 and 265 are -alternately conductive,pulses will appear at intervals of 0.02 second on each of the anodesthereof in response to alternate 0.01 second pulses applied to theirgrids. The pulses from tube 262 are applied by Way of condenser 275 andresistor 276 to the grid of an amplier tube 277.

The anode of amplier 277 is coupled by wayof condenser 278 and resistor279 to the control electrode of the gas discharge tube 280. While otherthyratron type tubes may be suitable for operation as tube 280, aprelferred type of gas discharge tube, the type OAS, has inherent in itsoperation a greater impedance discontinuity when red and thus provides alarger output pulse than other well known thyratrons. As illustrated,signals from tube 277 are applied to the suppressor grid, of tube 280.The screen grid in accordance with preferred operation of type OA tubeis floating and the control grid is connected by way of resistor 283 toa point of positive potential. The anode of tube 280 is connectedthrough the primary of a pulse transformer 281 and a condenser 282 toground. Tube 280 normally is nonconducting. During the periods that itis extinguished, current ows from battery 284 connected in the anodecircuit oftube 280 through the primary of transformer 281 to chargecondenser 282. When a pulse is applied to the suppressor grid of tube280, condition is initiated therein and condenser 282 dischargestherethrough producing a high voltage pulse in the secondary oftransformer 281.

The secondary of pulse transformer 281 is connected to ground and t-othe igniter electrode 285 of a gas tube .286. Electrode 287 of tube 286is connected to ground and also by way of condenser 288 to the electrode289.

.Electrode 289 is connected by way of resistor 290 to the 18 B+ terminalof a Ysuitable voltage source such as battery 284.

`In a similar manner the anode of tube 265 is connected through triode291, pentode 292 and pulse transformer 293 to a second gas or flash tube294. When a pulse appears on the igniter electrodes of tubes 286 and294, condensers- 288 and 288a discharge through their -respective tubesto produce short brilliant ashes of light. The pulsed light Vis focusedby a suitable optical system (not shown but provided in the recorder 45)to project an extremely narrow beam of short time duration ontophotographic recording tilm comprising record 10a. By way of example,tubes 286 and 294 may be of the type manufactured and sold under thetrade name Strobatron, type SA-309, by Sylvania Electric Products, Inc.,Emporium, Pennsylvania.

In operation, tube 289, in response to 0.01 second pulses applied atterminal 260, will be energized at 0.02 second intervals. Tue 294, inresponse to application of 0.01 second pulses at terminal 260, will 'beenergized at 0.02 second intervals but delayed a 0.01 second intervalfrom the energization of tube 286. Thus tubes 286 and 294 flashalternately to produce a series of 0.01 second markers on the recordingmedium in Vrecorder 45.

The pulses occurring at intervals of 0.1 second and `appearing onchannel 259 are applied by way of condenser 295 -and resistor 296 to thegrid of triode 277 and by way of condenser 297 and resistor 298 to thegrid of -tube 291 to provide simultaneous energization of both ash tubes286 and 294 at 0.1 second intervals. A

As a result of operation of the system of Fig. 8, a record 10a, Fig. l,is produced which has a trst timing line corresponding with the recordzero instant or initial timing marker and which has relatively lighttiming lines -every 0.01 second thereafter with heavier or reinforcedlines every 0.1 second. For clarity, only the ends of the 0.01 timinglines have been shown. Not only does the record have the `distinctivecharacteristics above noted, but such timing lines occur in the samerelation with respect -to the seismic information on the new record asoccurrence of the original seismic event in time.

The foregoing description includes the various individual steps involvedin a single cycle of operations, or, stated otherwise, during a singlecycle of travel of the record 210 past the transducer 213. I=f record210 is a continuous loop, the display on oscilloscope 222, Fig. 7, maybe made to be a repetitive phenomena synchronized through the abovedescribed timing system with the repetitive production of signals fromrecord 210. To provide for -resetting the circuits at the end of eachdisplay period and facilitate repeated presentation of recorded data, apulse is applied `from the oscilloscope 222 to the control grid of tube241, Fig. 6. The horizontal sweep voltage from oscilloscope 222 isutilized. A pulse is derived, by means not shown, from the sweep voltagecoincident with the flyback or return of the cathode beam to its zeroIposition. Circuit 300 serves to transmit this pulse to the control gridof tube 241. Tube 241 is then rendered non-conductive, and conductionthrough tube 235 is initiated, closing gate 228.

Coincident with the initiation of conduction in tube 235, the anodevoltage on all tubes in the ring counters 251-254 is momentarily reducedas explained below to extinguish all the counter tubes. 'Ihereafter thezero tube in each of the rings is rendered conductive and ready for `asucceeding cycle of operations.

More particularly, the anode voltage on the ring counters is derivedfrom a suitable source such as the battery 301. Current for the ringcounters flows from the positive terminal of battery 301 throughresistor 302 and conductors 303 and 304. Conductor 304, shown connectedonly to the anodes of ring counter 251, will also be connected to theanodes of the tubes in the ring counters 252-254. For simplicity, the`details of the remaining ring counter are omitted. The resistor 302,

played on the oscilloscope.

high current fiow through tube 306 abruptly reduces the `voltage at itsanode to a low level, i.e. to approximately 8 volts for conventionalthyratrons The latter voltage appearing on conductor 304 and applied tothe anodes of each of the tubes in the ring counters is insufficient tomaintain conduction therein. Condenser 307, initially charged to thepotential of battery 301, discharges through tube 306 and controls theinterval that Itube 306 is conducting. The conduction time is determinedby the time constant of the condenser discharge circuit comprising thecondenser 307, resistor 308 and the anode-cathode impedance of tube 306.Thus tube 306 is extinguished shortly after it is fired. As condenser307 recharges, the voltage on conductor 304 rises to the potential onthe anode of tube 306 and is then sufficient for subsequent operation ofthe ring counters.

Not only must all of the tubes of the ring counters be extinguished atthe end of each cycle of display on the cathode ray oscilloscope, asabove described, but in addition the zero tube in each ring must befired in preparation for a succeeding cycle of operation. To this endthe change in voltage of the anode of tube 306 is applied, after asuitable time delay in the circuit 310 to the grid of tube 311.

The gas diode 310:1, a neon ltube having a breakdown potential somewhatabove the voltage across tube 306 when it is conducting, provides ashunt for modulation pulses appearing on conductor 304 when the ringcounters are in operation and when tube'306 is nonconducting. However,when tube 306 fires, tube 310a, which when conducting presents a verylow impedance, is extinguished thereby giving to the resistors andcondensers in the circuit 310 the control of the time delay oftransmission of a pulse to the tube 311.

The resultant change in anode voltage of tube 311 is coupled by way ofcondenser 312, rectifier 313 and resistor 314 to the screen grid of thezero tube in ring counter 251. Similarly, the output of tube 311 iscoupled through rectifier-resistor combination 315 to the zero l tube ofring counter 252 and by way of the rectifierresistor circuit-316 to thezero tube of ring counter 253. In a similar manner the zero tube of ringcounter 254 is fired for a succeeding cycle. Thus application of thesingle pulse from tube 311 places all of the ring counters in conditionfor operation starting from their zero tube.

It will now be apparent that the single cycle of operations abovediscussed in detail will be repeated cyclically as the record element210 is driven past the transducer 213 repeatedly to produce the threesets of output signals, the signals corresponding with the recordedseismic waves, with the constant frequency time base signal and with thetiming marker pulse in order to present on the face of the oscilloscope222 a pictorial representation of such signals, thereby permittingmanipulation of the filtering characteristics of amplifiers 21S-220 toproduce a record of optimum filtering characteristics. lf the sweep onthe oscilloscope 222 is caused to be relatively slow and the selectorswitches on all of the ring counters are set on zero position, theentire record may be dis- If the sweep is caused to have a much highervelocity, the selector switches on the ring counters may then bemanipulated to present in detail selected short sections of the recordon the oscilloscope. When an operator is satisfied as to the filteringaction, the selector switches on the ring counters 251 and 252 will beset on zero positions so that following the timing marker output pulseswill be applied to terminal 258a every 0.01 second and will be appliedto .terminal 259a every- 0.1 second. Thus the original seismogram 10,Fig. l, is repeatedly scanned and exhibited on the display means. On aselectable cycle of display of the record, the operator may manuallyclose an energizing circuit to the recorder 45 and maintain it closedfor a period long enough to record the entire duration of the displayedor exhibited signals on the new or secondary seismogram 10a.

The foregoing description sets forth in detail a ree recording systembased upon the existence of a primary record preferably of magneticcharacter for the production of secondary records on photographic paperhaving variable amplitude traces. It will now be apparent that thesecondary records themselves may be phonographically reproducible inform and that other modifications may be made without departing from thepresent invention. Operation has been described as specifically relatingto an initial marker repeatedly referred to as a time break signalgenerated in time coincidence with the generation of seismic waves. Aninitial marker of this character is almost universally employed inconnection with reflection seismic exploration. However as is wellunderstood by those skilled in the art, an initial marker other than atime break signal may be utilized, so long as the time relationship ofsuch initial marker to the instant of generation of the seismic waves iswell known or can readily be calculated. For example, an uphole geophonesometimes is utilized in place of a time break for certain-purposes andas such may be utilized in place of the time break as the initial markerherein described. Further, in connection with refraction seismographexploration, first arriving energy often is used as an initial markerand as such may serve in that sense for use as herein described. Othersuch modifications may now suggest themselves to lthose skilled in theart, and it is intended to cover such modifications as fall within thescope of the appended claims.

We claim:

l. A system for studying a phonographically reproducible record of atransient wave having associated therewith a periodic time base signaland an initial marker positioned in predetermined time relation to thegeneration of said transient which comprises means including transducermeans for cyclically scanning said record repeatedly to produce on ascaled time base a first signal corresponding to said transient, asecond signal corresponding to said periodic time base signal, and athird signal coincident and corresponding with said initial marker,monitoring means including a signal channel and a control channel,circuit means interconnecting said transducer means and said signalchannel for application to said monitoring means of repeated cycles ofsaid first signal, a normally 4non-conductive unit having outputterminals and connected at its input to said transducer means andresponsive to said second signal, circuit means interconnecting saidtransducer means and said normally non-conductive unit and responsive tosaid third signal for rendering conductive said normally nonductive unitin each cycle of said first signal at a time coincident with said timingmarker for transmission therethrough of said second signal, a pulseselective circuit connected between said output terminals and saidcontrol channel for applying to said monitoring means a selected cycleof said second signal for actuating said monitoring means to render itresponsive to said first signal, and means operable in the intervalfollowing said selected cycle of said second signal and prior to thebeginning of the next succeeding cycle of said first signal to rendersaid unit non-conductive.

2. A system for studying a phonographically reproducible record of atransient wave having associated therewith a periodic time base signaland an initial marker having a predetermined time relation to thegeneration of said transient which comprises means including transducermeans for cyclically scanning said record repeatedly to produce on ascaled time base a first signal corresponding to said transient, asecond signal corresponding to said periodic time base signal, and athird signal coincident and corresponding with said initial marker,monitoring means having a signal channel and a control channel, circuitmeans interconnecting said transducer means and said signal channel forapplication -to said monitoring means of repeated cycles of said tirstsignal, a normally non-conductive unit having output terminals andconnected at its input to said transducer means and responsive to saidsecond signal, circuit means interconnecting said transducer means andsaid normally nonconductive unit and responsive to said third signal forrendering conductive said normally non-conductive unit in each cycle ofsaid irst signal at a time coincident with said third signal fortransmission therethrough of said second signal, a pulsel selectivecircuit connected between said output terminals and said control channelfor applying to said monitoring means a selected cycle of said secondsignal for actuating said monitoring means to render it responsive tosaid lirst signal, and means responsive to said monitoring means forrendering said unit non-conductive in the interval following saidselected cycle of said second signal and prior to the beginning of thenext succeeding cycle of said iirst signal.

3. A system for studying a record of a transient wave occurring in timefollowing an initial instant which comprises means for cyclicallyproducing a voltage which varies in accordance with said transient,means for generating an initial marker coincident and corresponding withsaid instant, a monitoring means having a signal channel and a controlchannel, means for applying said transient to said signal channel, anormally blocked Acounter system including a source of periodic signalswhose frequency is higher in -a predetermined relation than thefrequency of cyclic reproduction of said transient, said counter alsoincluding a plurality of decimal counters characterized by fundamentalperiods differing one from the other by factors of ten and adjustablemeans in each counter for selecting any digit between one and ten, meansresponsive to said initial marker for energizing said counter system,means `for connecting said counter system to said monitoring means toapply -a selected cycle of said periodic signalV thereto to initiatepresentation of the pontion of said transient beginning at a timedetermined by said adjustable means of said counters, and means forapplying to said counter system a pulse in the interval between saidsingle cycle and the beginning of nfthe next succeeding cycle of saidtransient for resetting said counter system.

4. A system for studying a phonographically reproducible record of atransient wave having associated ytherewith a periodic time base signaland an initial marker positioned in predetermined time relation .to thegeneraton of said transient which comprises means including tnansducermeans for cyclically scanning said record repeatedly to produce on ascaled time base a lirst signal corresponding to said transient, asecond signal corresponding to said periodic time base signal, and athird signal coincident and corresponding with said initial marker,montoring means including a signal channel and a control channel,circuit means interconnecting said transducer means and said signalchannel for rapplication to said monitoring means of Vrepeated cycles otsaid rst signal, a normally non-conductive unit having output terminalsand connected at its input to said transducer means and responsive tosaid second signal, circuit means interconnecting said transducer meansand said normally non-conductive unit ,and responsive to said thirdsignal for rendering conductive said normally non-conductive -unit in aiirst cycle of said first signal at a time coinci ent with said initialmarker for transmission therethrough of said second signal, a pluralityof gas tubes each having a iringterminnl connected to an adjacent tubeto form a l'closed loop, a signal input circuit for said loop connectedsaid output terminals and to said tiring terminals for shiftingconduction from one tube to another in response to said second signal, asource of anode supply voltage having a positive terminal and a negativeterminal, an impedance means connected to said positive terminal and tothe anodes of -all of said gas tubes, a thyratron having a grid, acathode connected to said negative terminal and an anode connected tothe anodes of said gas tubes, a condenser connected between said anodesand said negative terminal for accumulating a charge from said source,an output pulse selector having a zero output position connected to thecathode of the iirst of saidfgas tubes and a plurality of outputpositions connected respectively to the cathodes of the remaining gastubes for transmitting to said control channel a pulse spaced aninterval after said initial marker determined by the frequency of saidsecond signal and the setting of said output pulse selector to rendersaid `monitoring means responsive to said first signal, means forapplying a reset pulse to said normally 'below their conduction voltage,a circuit connected between said anodes and the tiring terminal of saidlirst gas tube for transmission of a pulse produced in time-coincidencewith said reset pulse, and means in said last named circuit for delayingsaid last named pulse in a time interval greater than said period tolire said iirst tube preparatory for a second cycle of said iirstsignal.

5. A system for studying a phonographically reproducible record of atransient wave having associated therewith a periodic time base signaland an initial marker positioned in predetermined time relation to thegeneration of said transient which comprises means including transducermeans for cyclically scanning said record repeatedly to produce on ascaled time base a lirst signal corresponding to said transient, asecond signal corresponding to said periodic time base signal, and athird signal coincident and corresponding with said initial marker,monitoring means including a -signal channel and a control channel,circuit means interconnecting said transducer means and said signalchannel for application to said monitoring means of repeated cycles ofsaid iirst signal, a normally non-conductive unit having outputterminals and connected at its input to said transducer means andresponsive to said second signal, circuit means interconnecting saidtransducer means and said normally non-conductive unit and responsive tosaid third signal for rendering conductive said normally non-conductiveunit in a first cycle of said first signal at a time coincident withsaid timing marker for transmission therethrough of said second signal,a plurality of gas tubes each having a :tiring terminal connected to ainadjacent tube to form a closed loop, a signal input circuit for saidloop connected to said output terminals and to said firing `terminalsfor shifting conduction from one tube to another in response to saidsecond signal, a source of anode supply voltage having a positiveterminal and a negative terminal, an impedance means connected to saidpositive terminal and to the anodes of all of said gas tubes, athyratron having a grid, -a cathode connected to said negative terminaland an anode connected to the anodes of said gas tubes, a condenserconnected between said anodes and said nega-tive terminal foraccumulating a charge -from said source, an' output pulse selectorhaving a zero output posi-tion connected to the cathode of the tirst ofsaid gas tubes and succeeding output positions connected respectively tothe cathodes of succeeding gas tubes for transmitting to said controlchannel a pulse spaced an interval after said initial marker determinedby the frequency of said second signal and the setting of said outputpulse selector to render said monitoring means responsive to said iirstsignal, means for applying a reset pulse to said normally non-conductiveunit and to said grid in predetermined 'time relation to said selectedpulse for discharge of said condenser through said thyratron in a perioddepending upon the time constant of the condenser- 'thyratron circuit tolower the voltage on the anodes of said gas tubes below their conductionvoltage, a reset circuit connected between said anodes and the firingterminal of said lrst gas tube for transmission of a pulse produced intime-coincidence with said reset pulse, mearns in said last namedcircuit for delaying said last named pulse in time interval greater thansaid period to fire said first tube preparatory for a second cycle ofVsaid rst signal, and a voltage sensitive impedance elementnon-conductive at the conduction-voltage of said thyratron andconductive at the conduction voit-age of said gas tubes connected incircuit between said -anodes Iand ground and elective to shunt allpulses in said anode circuit other than said reset pulse.

6. A system for studying and `for recording on a recording mediumseismic signals initially recorded together with a timing signal on aphonographically reproducible record which comprises translating meanscoupled to said record for generating electrical signals correspondingwit-h said seismic signals and for producing pulses from said timingsignal at a rate related to the time duration of said seismic signals bya scaling factor, a. visual display means, a recording means adapted todrive said recording medium past a recording point, a transmissionchannel for said electrical signals connected between said translatingmeans and -both said display means and said recording means, circuitmeans operable in response to said pulses `for applying a timingfunction to said display means and to said recording means, said circuitmeans including adjustable means for selectively applying said timingIfunction to said display means and to said recording means coincidentwith a selected one of said electrical pulses within the periodcorresponding to said time duration.

7. A system for studying and for recording on a recording medium seismicsignals initially recorded together with a timing signal on aphonographically reproducible record which comprises translating meanscoupled to said record for generating electrical signals correspondingwith said seismic signals and for producing pulses Ifrom said -timingsignal at a rate related to the time duration of said seismic signals bya scaling factor, a visual display means, a recording means adapted todrive said recording medium past a recording point, a transmissionchannel for said electrical signals connected between said translatingmeans Iand both said display means and said recording means, a timingcircuit interconnecting said translating means and said display meansand said recording means, said timing circuit including means actuatablein response to said pulses for impressing a space scale on saidrecording medium as it is driven past said recording point, and meansactuatable in response to a selectable one of said pulses for initiatingthe `operation of said display means.

8. A system for re-recording a phonographically reproducible record o'fseismic waves together with an initial marker recorded coincident withgeneration of amd seismic waves and with a time base signal whichcomprises signal producing means responsive to said record having threeoutput signals respectively corresponding to the record of said seismicwaves, said time base sign-al and said initial marker, a transmissionchannel for the rst of said three output signals, a recorder having arecording medium driven past a recording point and connected to saidtransmission channel for impressing the first of said signals on saidmedium, a normally non-conductive channel yfor the second of said threeoutput signals, a circuit responsive to the third of said three outputsignals for rendering conductive said normally non-conductive channel,and means connected between said normally non-conductive channel andsaid recorder for applying the second of said three output signals tosaid recording 24 medium at said recording point in a space relationwith respect to the rst of said signals as said time base is related tosaid seismic signals.

9. A system `for re-recording a phonographically reproducible record ofseismic waves together with an initial marker recorded coincident withgeneration of said seismic waves and with a time base signal whichcomprises signal producing means having three output signalsrespectively corresponding with the record of said seismic waves, saidtime base signal and said initial marker, amplifying means for the rstof said three output signals h-aving a predetermined amplitude-frequencycharacteristic -for producing modified signals, a recorder connected tosaid `amplifying means for producing a record of said modied signals, anormally non-conductive channel lfor the second of said three outputsignals, a circuit responsive to the third of said lthree output signalsfor rendering conductive said normally non-conductive channel, Iandmeans connected between said normally nonconductive channel land saidrecorder for applying the second of said three output signals theretorelated to said modiiied signals as said time base is related to saidseismic signals.

10. A system for re-recording a phonographically reproducible record ofseismic waves together with an initial marker recorded coincident withgeneration of said seismic waves and with a time base signal whichcomprises signal producing means having three output signals, the iirstcorresponding with the record of said seismic waves, the secondcomprising electrical pulses repeated in time in accordance with andderived from the record of said time base signal, and the third acontrol pulse corresponding with said initial marker, -a recorder havinga recording medium driven past a recording point and a pair of lightsources adjacent said recording point, a transmission channel connectedto said recorder and to said signal producing means responsive to saidfirst output signal for recording said iirst signal on said recordingmedium, a normally non-conductive channel for said second output signal,a circuit responsive to said third output signal connected to saidnormally non-conductive chan-nel to render it conductive coincident withgeneration of said third signal, and frequency dividing means for saidelectrical pulses connected between said normally non-conductive channeland said light sources for applying pulses at a first rate alternatelyto said pair of light sources and `for applying pulses at a selectedsub-rate simultaneously to both of said light lsources for exposing atlow and high intensity respectively portions of said recording mediumsuccessively positioned at said recording point as a scale related tosaid first signal impressed on said medium as said time base is relatedto said seismic signals.

1l. A system for re-recording a phonographically reproducible record ofseismic waves together with an initial marker recorded coincident withgeneration of said seismic waves and with a time base signal whichcomprises signal producing means having three output signals, the -tirstcorresponding with the record of said seismic waves, the secondcomprising electrical pulses repeated in time in accordance with andderived from the record of said time base signal, and the third acontrol pulse corresponding with said initial marker, a recorder havinga recording medium driven past a recording point and a pair oftransducers adjacent said recording point, a transmission channeconnected to said recorder and to said signal producing means responsiveto said first output signal `for recording said tirst signal on saidmedium', a normally non-conductive channel for said second outputsignal, `a circuit responsive to said third output signal connected tosaid normally non-conductive channel to render it conductive coincidentwith generation of said third signal, and frequency dividing means forsaid electrical pulses connected between said normally non-conductivechannel and said transducers 'for applying pulses at a iirst ratealternately osnse 25, Yto said transducens and for applying pulses at aselected sub-rate simultaneously to both of said transducers forimpressing indications on said medium `at low intensity and highintensity the portions successively positioned at said recording pointas a scale related to said first signal impressed on said medium as saidtime base is related to said seismic signals.

12. A system for producing a space scale on a recording medium as it isdriven past a recording point which comprises a pair of recordingtransducers adjacent said recording point, means for producing controlpulses repeated in time, circuit means for applying said pulses `firstto one and then to the other of said transducers to impress lowintensity indications at points of a iirst spacing on said medium asthey are successively positioned at said recording point, pulse dividingmeans responsive to each of said control pulses for producing outputpulses therefrom at a selected lsub-multiple of the frequency of saidcontrol pulses, and means for applying said output pulses to both ofsaid transducers simultaneously to impressre- Alatively high intensityindications at points of a second spacing onV said medium related tosaid first spacing as Asaid sub-multiple is related to the frequency ofsaid control pulses distinctively to mark said scale.

13. A-system for producing a space scale on a photographic filmv as itis driven past a recording point which comprises a pair of light sourcesadjacent said recording point, means for producing control pulsesuniformly repeated in time, circuit means for applying said pulses firstto one and then to the other of said light sources to ex-l pose at lowintensity points of -a first spacing on said film as they aresuccessively positioned at said recording point, pulse dividing meansresponsive to each of said control pulses for producing output pulsestherefrom at a selected sub-multiple of the frequency of said controlpulses, and means 4for applying said output pulses to both of saidsources simultaneously to expose at relatively high intensity' points ofa second spacing on said lm related to said first spacing as saidsub-frequency is related to the frequency of said control pulsesdistinctively to mark said scale. f

14. In a system in which electrical control pulses are -repeated in timefor producing a space scale on a photographic film as it is driven pasta recording point, the improvement which comprises a pair of lightsources adjacent said recording point, a circuit for actuating first oneand then the other of said sources in response to said .control pulsesfor producing light flashes coincident with -each of said control pulsesto expose at low intensity points on said film successively positionedat said recording point to impress a scale on, said film, an electricalcircuit responsive to each of said pulses for producing output pulsesrecurring at a selected sub-multiple of the frequency of said controlpulses, and means forrapplying 'said output pulses to both of saidsources for simultaneously. energizing both of said sources at saidsub-frequency to expose said film at a relatively high intensitydistinctively to mark said scale in a space-relation corresponding withthe time occurrence of said output pulses. g

"15. VA system for producing a space scale on a photographic film 'as itis driven past a recording point which comprises a pair of light sourcesadjacent said recording point, a source of control pulses, a circuit foractuating `first one Aandthen the otherV of said sources in response tosaid control pulses for producing light flashes coincident Vwith each ofsaid control pulses to expose at low intensityV points on said filmsuccessively positioned at said recording point to impress a scale onsaid film, a pulse dividing network responsive to each of said controlpulses for producing output pulses at a selected integral submultiple ofthe frequency of said control pulses, and means for applying said outputpulses to both of said sources for simultaneously energizing saidsources coincident with each of said output pulses to expose said hlm ata relatively high intensity distinctively to mark said 26 scale atpoints'spaced with respect to said points exposed at low intensity assaid sub-multiple is related to the frequency of said control pulses.

16. A system for producing a space scale on a photographic lm as it isdriven past a recording point which comprises a pair of light sourcesadjacent said recording point, a source of electrical control pulses, acircuit for actuating first one `and then the other of said sources inresponse to said control pulses for producing light ashes coincidentwith each of said control pulses to expose at low intensity the pointson said film successively positioned at said recording point to impressa scale on said film, a decadepulse dividing network responsive to eachof said pulses for producing output pulses recurring at one-tenth thefrequency of said control pulses, and means for applying said outputpulses to both of said sources for simultaneously energizing both ofsaid sources coincident with every tenth control pulse to expose saidfilm at a relatively high intensity distinctively to mark said scale ina space relation corresponding with the time occurring of said outputpulses.

17. A system for producing a space scale on a photographic iilm as it isdriven past a recording point which comprises a pairof light sourcesadjacent said recording point, two control-tubes connected to said lightsources, a source of control pulses, switching means interconnectingsaid source and said control tubes and actuated in response to saidcontrol pulses for transmission of succesive control pulses first to oneof said control tubes `and then to the other through said switchingmeans to expose at low intensity points on said vfilm sucessivelypositioned Yat said recording point, and a pulse dividing networkconnected between said source of control pulses and both of said controltubes for applying to both of said tubes simultaneously output pulsesrecurring at a selected sub harmonic of the frequency of said controlpulses to expose at high intensity points on said film spaced inthe samerelation as points exposed at low intensity as said sub-harmonic bearsto its fundamental.

18. A system for impressing on a recording medium seismic signalsinitially recorded with a timing signal on a phonographicallyreproducible record which comprises translating means coupled to saidrecord for generating electrical signals corresponding with said seismicsignals and for producing electrical pulses at a time rate related tothe time duration of said seismic signals by a scaling factor, arecorder including means for driving said recording medium past arecording point, means including a pulse counting circuit connected tosaid translating means and actuated in response to said electricalpulses for irnpressing a space scale on said recording medium as it isdriven past said recording point, and a transmission channel connectedbetween said translating means and said recorder for impressing saidelectrical signals on said recording medium as it is driven past saidrecording 'point in a space relation related to said time duration bysaid scaling factor.

19. A system for impressing on ya recording medium seismic signalsinitially recorded with a timing signal on a phonographicallyreproducible record which comprises translating means coupled to saidrecord for generating electrical signals corresponding with said seismicsignals and for producing electrical pulses at ya time rate related tothe time duration of said seismic signals by a scaling factor, arecorder including means for driving said recording medium past arecording point, a pulse counting circuit connected to said translatingmeans, light-pulsing means connected to said counting circuit actuatedin response to selected ones of said electrical pulses for impressing aspace scale on said recording medium as it is driven past said recordingpoint, and a transmission channel connected between said translatingmeans and said recorder for impressing said electrical signals on saidrecording medium as it is driven past said recording point in a spacerelation related to said time duration by said scaling factor.

20. A system for impressing on a recording medium seismic signalsinitially recorded with a timing signal on a phonographicallyreproducible record which comprises translating means coupled to saidrecord as to permit relative movement therebetween for generatingelectrical signals corresponding with said seismic signals and forproducing electrical pulses at a time rate related to the time durationof said seismic signals by a scaling factor, a recorder including meansfor driving said recording medium past a recording point, meansincluding a pulse counting circuit connected to said translating meansand actuated in response to said electrical pulses for impressing onsaid recording medium as it is driven past said recording point a spacescale dependent upon said timing signal on said phonographicallyreproducible record regardless of the speed of said recording medium orthe relative movement between said phonographically reproducible recordand said translating means, and a transmission channel connected betweensaid translating means and said recorder for impressing said electricalsignals on said recording medium as it is driven past said recordingpoint in a space relation related to said time duration by said scalingfactor.

21. A system for studying and for recording on a recording mediumseismic signals initially recorded together with a timing signal on aphonographically reproducible record which comprises translating meanscoupled to said record for generating electrical signals correspondingwith said seismic signals and for producing pulses from said timingsignal at a rate related to the time duration of said seismic signals bya scaling factor, a visual display means, a transmission channel forsaid electrical signals connected between said translating means andsaid display means, a timing circuit interconnecting said translatingmeans and said display means, said timing circuit including meansoperable in response to a selectable one of said pulses for initiatingthe operation of said display means visually to show a portion of saidelectrical signals, recording means `adapted to drive said recordingmedium past a recording point, said recording means being connected tosaid channel and to said timing circuit to receive said electricalsignals and timing pulses to impress on said recording medium the spacescale, and means for initiating operation of said recording means torecord all of said electrical signals while a selected fraction thereofappears on said vdisplay means.

22. A system vfor clarifying seismic reflections appearing in aseismogram recorded on a phonographically reproducible record togetherwith a timing signal comprising visual means lfor displaying seismicsignals, means including a transducer for detecting said seismic signalsand applying them to said visual means, control means for said visualmeans operable by said timing signals for displaying that portion ofsaid seismogram including one of said reflections, means for modifyingthe seismic signals detected by said transducer for bringing into bolderrelief the nature of said reflection, and means for recording saiddetected seismic signals to produce a new seismogram -while observing onsaid visual means the clarified reflection to be studied.

23. rA system for clarifying seismic reflections appearing on aseismogram recorded on a phonographically reproducible record togetherwith a timing signal comprising visual means for displaying seismicsignals, and means including a transducer for detecting said seismicsignals and for applying them to said visual means, control means forsaid visual means including `a pulse counting system responsive to saidtiming signals and adapted to initiate in response to one of said pulsesdisplay of that portion 0f said seismogram including one of saidreflections, means for varying selected frequency components of theseismic signals detected by said transducer for bringing into bolderrelief the nature of said reflection, and means for recording saiddetected seismic signals to produce a new seismogram while observing onsaid visual means the clarified reflection to be studied.

24. A system for clarifying seismic reflections appearing on aseismogram recorded on a phonographically reproducible record togetherwith a timing signal comprising cathode ray means for displaying seismicsignals, and means including a transducer for detecting said seismicsignals and for applying them to said cathode ray means to deflect saidcathode ray in a first sense, control means for said cathode ray meansincluding a pulse counting system responsive to said timing signals andadapted to initiate deflection of said cathode ray in a second sense inresponse to one of said pulses to display that portion of saidseismogram including one of said reflections, means for modifyingselected frequency components of the seismic signals detected by saidtransducer for bringing into bolder relief the nature of saidreflection, and means for recording said detected seismic signals toproduce a new seismogram while observing on said cathode ray means theclarified reflection to be studied.

25. A system for visually analyzing a seismogram of the phonographicallyreproducible type having timing impulses uniformly spaced lengthwisethereof Which comprises means for generating a first set of electricalsignals representative of the seismic data recorded on said seismogramand for generating a second set of electrical signals corresponding innumber with the number of said timing impulses, means responsive to saidsecond set of electrical signals for initiating a count of said timingirnpulses at a time bearing a predetermined relationship with respect toa reference point on said seismogram representative of the instant ofgeneration of those seismic waves which were productive of the seismicdata on said seismogram, visual display means, means for applying saidfirst set of electrical signals to said display means, means operablewhen the count of said impulses reaches a predetermined value forinitiating the production on said display means of subsequentlyoccurring seismic data, means operable when the count of said impulsesreaches a second predetermined value for terminating the display of saiddata by said display means, and timing means in said display meanshaving a scanning time corresponding with the time interval scaled bythe passage of the timing impulses intermediate said predeterminedvalues.

References Cited in the file of this patent UNITED STATES PATENTS2,424,622 McClure July 29, 1947 2,496,392 Hasbrook Feb. 7, 19502,594,731 Connolly Apr. 29, 1952 2,609,143 Stibitz Sept. 2, 19522,648,822 Walter Aug. 1l, 1953 2,658,579 Rieber Nov. l0, 1953 2,672,944Minton Mar. 23, 1954 OTHER REFERENCES The Cathode Ray SoundSpectroscope, in Journal of the Acoustical Society of America, September1949, PP. 527-537.

Frequency Analysis of Seismic Waves, in Geophysics, October 1952, pp.721-738.

